Re:Ball Screw mounting block

Mike Gann wrote:<snip> Is this basically the way to

>do it?
>Also, is there any advantage to having this
>type of setup on each end of the X-Axis screw
>with a little tension applied to the screw, or just
>support the other end with a simple radial bearing.

Mike,

I've modified your drawing below. My addition is a spacer sleeve
between the bearings EXACTLY sized(length) in relation to the
thickness between the bores. This prevents the pre-loading nut you
described from doing damage to the bearings when it is tightened up.
This forms what is called(by most lead and ballscrew mfr's) a RIGID
mount.

Bearing Support Block (modified)
+---------+
| |
|--+ +--|
-------|--|---| |
| |---|--|+++
| | | |
| |---|--|+++
-------|--|---| |
|--+ +--|
| |
+---------+
Next step down is two bearings (faces ground to a matched
pair,eliminating "play", placed in a common bore.They are held
together with an internal nut(like a camera lens)and then the shaft
is fed thru and tightened with a nut as you described above. Mfr's
call this a FIXED mount.

The radial bearing by itself is called a SIMPLE mount.


Now to your second question: Yes.

All rotating shafts(lead and ballscrews included)have a diameter/
length/ speed/ mounting method relationship.

Using the different mounts (and in combinations) changes:
1. The safe speed for your assembly (preventing "whipping")
2. The safe distance between mounts (for "whipping" as above, and for
compression strength(the ability of the shaft in compression to carry
the load imposed))
3. The diameter of shaft needed. (better mounts mean a smaller
diameter shaft OR a greater distance between mounts for a given
diameter)

Ballendo

P.S.
For more info, (and the tables showing these telationships), get a
ballscrew mfrs' catalog. Names to try are Nook, Ball screws and
Actuators, Rockford Ballscrews, Lintech.